An anti-drainback valve (ADB) is a type of valve that is typically a component in spin-on oil and fuel filters. An ADB, when used in conjunction with oil filters, is designed to retain oil in a filter and to prevent the filter from being drained when the engine is not running. This ensures that the oil can achieve its full lubricating effect as soon as the engine is started.
ADBs are typically made from rubber. Rubber ADBs are often molded in silicon, nitrile, or other suitable rubber compounds in a two-part opening mold. A two-part mold is typically used for manufacturing ADBs because it is a cost-efficient process for producing a large quantity of ADBs based on their symmetrical shape.
Larger conventional spin-on filter assemblies typically employ ADBs that fit on a cap with a collared-type design. Such larger conventional filter assemblies are often used in locations where space restrictions are not an issue. An example of a large conventional filter assembly that utilizes a collar design can be found in U.S. Pat. No. 3,339,738.
There are certain situations and designs, however, that allow only for a very limited space for installing ADBs on oil and fuel filters in an engine. For example, engines on newer cars produced by companies such as Honda, Nissan, and Toyota have very limited space (about 75 to 90 mm) for mounting 65 mm diameter oil filters. Such space limitations have resulted in a difficulty in the installation of the conventional ADBs that utilize a collared cap design.
Plain caps (i.e., caps with relatively flat tops) have been designed for use on filter assemblies with tighter space limitations. Conventional ADBs used on filter assemblies utilizing such plain caps, however, do not lock into the caps securely. As a result, conventional ADBs may slip from the caps of the filter assemblies in rapid production assembly lines. This can cause a slowdown in production, and may even require a 100% inspection rate to ensure that slipped ADB filters do not reach customers.